Rigor Mortis is a condition that causes temporary stiffness of joints and muscles after a certain period after death.
In 2285, while investigating the Regula I station, Dr. Leonard McCoy discovered the bodies of several of the station's crew, who had been killed by Khan Noonien Singh and his Augments and determined that they had not yet undergone Rigor Mortis, indicating that they had not been dead long. (Star Trek II: The Wrath of Khan)